A NASA probe has become the first visitor to drop in on an ancient asteroid in billions of years.
After a journey of more than 80 million miles (130m km), Osiris-Rex is now about 12 miles (19km) away from Bennu, and will get ever closer, going into the asteroid's orbit on 31 December.
Spacecrafts have never before orbited a cosmic body as small as Bennu, which measures at just 500m (1,600ft) across.
Dante Lauretta, the lead scientist of the mission, tweeted he was "relieved, proud and anxious to start exploring!" following the arrival of the probe.
Osirus Rex is set to bring home the biggest haul of space materials since astronauts hand-delivered moon rocks to Earth in the 1960s and 1970s.
It has been chasing the diamond-shaped body for two years, and will orbit it for another year before scooping some gravel from the asteroid's surface and sending it back to Earth.
"For the past several months, Bennu has been coming into focus as I approached," the probe's Twitter account said.
"Now that I'm here, I'll fly around the asteroid and study it in detail. All the data I collect will help my team pick a spot to sample in 2020."
Scientists hope they will get to examine the contents of an astronomical time capsule, with the carbon-rich material taken from Bennu's surface holding evidence from the beginning of the solar system 4.5bn years ago.
They hope the robot will collect at least 60g (two ounces) of dust and gravel from Bennu, using a 3m (10ft) mechanical arm to hoover up particles.
The sample container will then break free from Osirus Rex and head towards Earth in 2021, parachuting down to Utah.
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Mr Lauretta said scientists were interested in "organic molecules that may have led to the origin of life and water-bearing minerals like clays" in their analysis of the asteroid.
Meanwhile, a Japanese probe is circling an asteroid named Ryugu, about double the size of Bennu, with a plan to bring home some specks of space dust.